The desirability of providing tiles with a shiny, durable, "no wax" protective coating has long been recognized. The problem has been to develop a process for coating tiles in high volume quickly and economically. This seemingly simple problem is complicated by several factors including the high cost of suitable protective materials, the presence on tile of decorative relief surfaces having high areas and low areas subject to different levels of wear, and the undesirability of applying protective materials onto the tile edges.
The straightforward approach of first coating large sheets with protective materials and then cutting tiles from the sheets is unduly wasteful of highly expensive coating material. Typically tiles are cut from wide sheets of flooring material such as vinyl or vinyl asbestos by what is known as the "in-line" or "picture-frame" process. In such cutting, a border of sheet material (resembling a picture frame) is left around each tile for permitting removal of the tile from the cutting die. While the material of the border can be recycled for its vinyl or vinyl asbestos content, any protective materials thereon are lost. Also lost are any protective materials applied to reject tiles. In view of the facts that protective coating materials can cost 18 to 25 dollars per gallon and millions of tiles are made each year, the resultant waste is substantial.
The coating of the tiles after cutting is complicated by the fact that one must coat the entire exposed surface, and yet avoid coating the edges. Coated edges are highly objectionable because they would prevent adjacent tiles from merging together when they are laid on surface such as a floor. Yet there is no readily apparent way to mask the edges compatible with high volume production.
In addition, the popularity of tiles with decorative relief surfaces has rendered many conventional coating techniques inappropriate. Such relief surfaces have high areas which, particularly in vinyl asbestos tile, are subject to greater than average wear and low areas which are subject to less than average wear. While all areas of the surface need some coating to maintain a uniform shiny appearance, a uniform thickness coating or a coating which is thicker in the low areas would be wasteful of the coating material.